The invention relates in particular to electro-chemical cells having an alkaline electrolyte in which at least one electrode includes a porous support made of metal, e.g. nickel, that is filled with active material, e.g. based on nickel hydroxide.
Such a porous support has a matrix structure comparable to a sponge in which the cells are connected to one another in a three-dimensional array, and it is referred to by the term "foam".
Before being filled with active material, the porosity of the foam of a support is greater than 90%. In its initial state, the thickness e.sub.1 of the foam used generally lies in the range 0.5 mm to 5 mm, depending on the application. After being filled, the thickness of the support is reduced, e.g. by compression or by rolling, to a thickness e.sub.2 that ensures good electro-chemical operation. At most, the above thickness reduction causes the initial thickness of the support to be halved.
An electrode plate of the above type is connected to a terminal of the cell via the head of the plate which includes an electrode connection zone. The connection zone is subsequently connected to said terminal by various means, e.g. screws or welding.
Problems arise in the making of a connection zone for an electrode having a foam type support: the connection zone must have adequate mechanical strength, must be a good conductor of electricity, must not make the plate heavy, and must be simple and cheap to make.
Various solutions exist for making the connection zone. These include, for example, riveting, stapling, or welding a metal part to the foam of the support; they also include taking a tongue made of a foam of the same kind but unfilled, and compressing it against the foam of the support after it has been filled with active material, and leaving 8 projecting tab, as described in document EP-A-0 418 774, for example. That solution is fragile and does not provide excellent electrical conduction in the head of the plate. Furthermore, none of the above solutions provides full satisfaction and they are all expensive.